The $3.9-billion shortfall that Sound Transit's financial experts have predicted is $767 million – or 5 percent – more than the deficit they projected last fall.

The board already ordered cost-cutting measures following that first grim revenue forecast. The agency cut into its reserves by $2.1 billion, trimmed administrative costs by $90 million, and implemented a sort of go-cheap policy that officials call "managing toward the low end of cost estimates."

"We have the ability to scale up and scale down to match our revenues, but we've trimmed all the fat," said Sound Transit finance director Brian McCarten. "There are going to be some tough decisions for the board."